Fastener driving apparatus



July 10, 1962 o. A. WANDEL ETAL FASTENER DRIVING APPARATUS Filed Feb. 16, 1959 IN V EN TORS 0501/? A. WANDEL AND y R/c/JARD H. [Pm LE ATTOEA/EYS rates Y This invention relates to a fluidroperated device for driving fasteners and, more particularly, to such a device including new and improved means for pneumatically actuating a fastener driving piston.

In most pneumatically operated tackers, staplers or 'nailers, a fastener is driven into a workpiece by a single power stroke of a blade actuating piston, which power stroke is initiated by the :abrupt admission of' a large body of compressed air into a cylinder under the control of manually or automatically actuated valve means. ,In some prior tools, the piston and the blade are returned to a normal position following the completion of the power stroke by a compression spring that is interposed between the lower end of the piston and the nose of the tacker. This arrangement has the disadvantages that the spring sometimes breaks and that the provision of the space required for the compression spring unduly increases the size of the gun and requires the blade to be located near the axis of the piston. To overcome these deficiencies, pneumatic means have been devised for restoring the piston to its normal position. To pneumatically actuated fastener driving tools which include both improved pneumatic driving means and a pneumatic piston return mechanism are shown and described in the copending application of Richard H. Doyle, Serial No. 642,143, filed February 25, 1957, now Patent No. 2,944,- 522, and in the copending application of Oscar A. Wandel and Richard H. Doyle, Serial No. 683,170, filed September 10, 1957, now Patent No. 2,979,725. However, it would be desirable to improve the reliability of operation of these tackers over a wider range of air pressure as well as to provide a hacker construction that is more economical to manufacture and easier to assemble.

Accordingly, one object of the present invention is to provide a new and improved fluid powered fastener driving apparatus.

Another object is to provide a fastener driving tool including new and improved pneumatic means for actuating a fastener driving blade.

Another object is to provide a fastener driving tool including new and improved means for supplying compressed air to a cylinder to actuate a piston.

A further object is to provide a pneumatically actuated tool including novel means for exhausting compressed air from a cylinder.

Another object i to provide a new and improved piston and blade assembly in which the position of the blade relative to the piston can be easily adjusted.

. Another object is to provide a pneumatically actuated hand tacker that is more easily manufactured and assembled.

In accordance with these and'many other objects, an embodiment of the invention comprises a housing which has an open upperrend and which defines both a lower chamber of lesser diameter and an upper chamber of greater diameter to which compressed air is supplied. A cylinder is slidably mounted in the uppermost chamber and slidably receives the flanged upper end of a piston, the lower portion of which is slidably mounted in the lower chamber. A fastener driving blade is secured to the lower end of the piston displaced from the axis thereof. The upper opening in the housing is sealed by a closure cap to which an annular resilient valve seat is secured-by a flanged member forming a part of an ex- 7 3&43372 Patented July 10, 1962 haust valve assembly. This member includes an axially extending passageway which is aligned with the axis of the piston and which provides an exhaust passageway for the upper portion of the cylinder. A spring carried on the member biases an exhaust valve element toward a position closing this passageway to seal off communication between the atmosphere and the uppermost chamber. A valve operator secured to the valve element extends into the upper chamber and is adapted to be engaged by the upper end of the cylinder to move the valve ele ment so that the exhaust valve assembly is opened.

In the normal condition of the pneumatically actuated tool, a manually controlled valve and a safety valve assembly are in a normal condition in which compressed air derived from a reservoir formed in a hollow handle of thehousing is supplied to the lower end of the upper chamber. This compressed air acts on thelower end of the cylinder to pneumatically bias the upper end of the cylinder into engagement with the valve seat, thereby to seal oiicommunication between the upper end of the interior of the cylinder and the upper chamber. In this to pneumatically maintain the piston inran uppermost position adjacent the upper end of the cylinder.

When manually controlled valve and the safety valve assembly are both actuated, the compressed air supplied to the lower portion of the upper chamber is cut off,

and/this portion of the upper chamber is connected to the atmosphere. This exhausts the compressed air from the lower portion of the cylinder and produces a pressure diiferential across the cylinder so that the cylinder is moved downwardly out of engagement with the valve seat. Asthe cylinder moves downwardly, the spring in the exhaust valve assembly shifits the valve element into engagement with a valve seat to close the exhaust valve.

' Further, as the cylinder moves downwardly, the upper portion of theinterior of the cylinder is abruptly. placed in communication with the large body of compressed air contained in the upper chamber so that the piston is driven downwardly in a power strokeduring which the fastener driving blade engages and drives a fastener supplied by a suitable magazine.

When the safety valve assembly and the manual valve are released, compressed air is again supplied to the lower portion of the chamber.. This compressed air produces an upwardly directed force acting on the cylinder to again shift the upper end of the cylinder into seating engage- 'ment with the valve seat so that communication between the upper chamber and the interior of the cylinder is closed off. Further, in moving upwardly, the upper end of the cylinder engages the valve operator element to open the exhaust valve assembly. The compressed air entrapped in the upper end'of the cylinder is then exhausted so that the piston is elevated to its normal position by the compressed air supplied to the lower end of the upper chamber. Thus, in response to each momentary actuation of the safety valve assembly and the manual valve, the piston is driven downwardly in a power stroke during which a fastener is driven into a workpiece and the piston is then pneumatically returned to its normal position.

Many other objects and advantages of the present invention will become apparent from the following detailed description when considered in conjunction with thedrawings in which:

FIG. 1 is a fragmentary sectional view of 'a pneumatically operated tacker v'eiitien 'and which' is"illustra't ed in its normal position; and

--F-L G. 2 is a fragmentary sectional view similar to FIG. -1 ftheitacker in 'its'p'osiu'on at the completion of apeerstroke; '1 r 1R ferring new more specifically to the drawings, thereshown ia pn'euinatically operated fastener driving fool; .mdicated generally as'10, which includes a housing 1" "having'an' en end and defining a lower cylindrical 141oflesser diameter and an upper cylindrical chamber '16 of greater diameter. Compressed air is sup jvlie to the nppferchamb'er' 16 from a reservoir formed by" ahollovv handle ,(not, shown) in-the housing 12 throughariicnlarged passageway 18. 'A cyhnder 20 that tssraably' nioimitedjinithe upper chamber 16 slidably portion of a piston 22, the lower portion jvhich sTslidably mounted. in the chamber 14. A g

driving blade 24 secured to the lower end of ni22is .adapted toiengage and drive fasteners, tapl es of nails, supplied by a suitable magazine 'iThefopenupper end of the chamber 16 is p emovable closure cap26 on'which a resilient ynve seat 2fiiandanfexhaust"valveassembly 30 are In'the norm condition of the ltool 10, a safety valve assembly 32 and amanu'ally controlled valve assembly'34 areitioth ir'iarjeleased condition sothat compressed air is :supplied to the lower end of the chamber 16 from the pas- 'isa' ew'ay 18. is compressed air forces the cylinder 20 to its uppermost position in which its upper end engages thejvalve seat 2810' close fofi communication between the interior of lthecylinder 20 andth'e chamber 16. In this positiom the upperend of the cylinder 20 also actuates ",the exhau's't valve" assembly 30 to an open condition in fwhichtlieiatmosphere is in communication with the in- ;teriof'of theicylinder. iThe .compressediair supplied 'to ."fihe lowerend fofthe' chamber '16 also acts on' the piston 22 holdit m' nelevateaer normal position;

ed nolonger supplied to. the lower end of Her and this portion of the chamber is conthe'atmosphere. This produces a downwardly .movesi downwardly away from' the closure cap v downwardly,the upper end of the cylinthje exhails't valve assembly 30 to close r, ,7 jou ti',of"engagement with the 'valve'seat' 28 'so that eompre ssd" air from the chamber 16 enters vjthe'cylinder 20,to,for ce t he piston 22 downwardly. During this power ston'" 22 remains in this displaced or lower positilsuichnrne a's 'both bfrhevaweasse bnes 32 and released. Therelease of these yalve assemblies sup- P ies ompr'esfsed'jair to the lower portion or theehamber i p the paksagewayj 18 so that'the jcylinder 20 is again ed 11 ardly'fto engage the valveseat 28 and to close xhaust valve 'assembly'lll S6,}l'h3t the interior of the joy gler'20 lis'iplaeed-in communicationTwiththe atmosphere. The venting of the upper 'portion' of thecylinder Z lbgctherp with theprovisi n of compressed air to the 119W?? l plft' on' hf the interior of this cylinder elevates the 'p' toni22 toiits'normal'positiom Thetool loremains'in arefnextiaef lated. f 7 Referring "now more spec'flcally to. .the housing 12, which may be cast of asuitahlefmaterial such asalumil lil or magnesium, the lower cylindrical chamber14 is ijthi ndineninnm Eothofthe ave assemblies 32 and i i l t l e net t s i a l o ida l e ves '"lowerportion of the piston 22. The lowerend of the chamber is provided with a resilient bumper 36 for cushionin the "terriiifieitidnof thepower stroke of the which embodies the present inure wo valveiassemblies 32'and 34 are actuated,

diiie'reiitial' across the cylinder 20 so that the "nt the compressed air in the upper portion of the her 16 -escaping to the atmosphere and also.

'owe'rendoflthe' blade24engages and 4 7 piston 22. The resilient bumper 36 is provided with a notched or grooved portion 38 for receiving the driver blade 24, and the lower end of the housing 12 is also provided with an opening 40 aligned with the notch 38 to 5 permit air to be exhausted from the chamber 14 when the ,piston 22 moves downwardly. The upper end of the chamber 14 is'connected to the lower endof the chamber 16 by an annular wall surface 42 which serves as 'a'stop to limit downward movement of the cylinder 20. j

withinvthe upper chamber 16, a sleeve 44 is secured within the chamber 16 to rest on an annular shoulder'46. One resilient O-riug 48 carried on the sleeve 44 provides a seal between the inner Wall of the chamber 16 and the outer wall of the sleeve 44, and another resilientO-ring 50 carried on the sleeve 44 provides a-seal between the inner wall of the sleeve 44 and the "outer wall of the cylinder 20. The cylinder 20 is slidably mounted withinthe sleeve 44 and includes a lower' annul'arflanged portion 20 .2941 which is looatedbetween the lower end of the sleeve 44 and the annular wall 42. 'A resilient O-ring 52 carried on the flanged portion 20a provides a seal between the inner wall of the chamber 16 andthe flanged portion or the cylinder 20. The annular space bounded by the lower end of the sleeve 44 and the upper surface of the flanged portion 20a is continuously connected to the atmosphere' through an opening 54 in the housing 12. The closure cap 26 "closesthe open upper end of the chamber 16 and provides the sole support for the exhaust valve assembly Mind the resilient'valve seat 28. The closurecap 26 is threadedly secured to the housing 12 with an O-ring 56sealing the connection therebetween. The valve element 28 is'secur'ed on the closure cap26 by a flanged element 58 which is received within a centrally 35 disposed opening in the cap 26. The element 58 is secured to the closure cap by a plug 60 having adepending "externally threaded portion 6012' which engages an internally threaded recessed portion 62 in the element 58. 'Thus, when the plug 60 is threadedly engaged with the mem-ber' 58 and tightened, the resilient valve seat '28 is clamped withina recess 64 in the-lower wall of the closure cap 26' by the flanged portion of the element 58.

' The element 58 and the plug 60 also form apart of the exhaust valve assembly 30which selectively exhausts compressed air from the upper end of the cylinder 20 when this cylinder is returned to the normal position shown in FIG. 1 at the conclusion of a power stroke. The exhaustivalve assembly 30 includes a valve element 66 that is movably mounted within a passageway 68 which is formed in the element'58 and which is in communication with the recess 62. A compression spring 70 located within a recess 72 in the depending. portion a of the plug 60 engages the upper end of the valve "element 66 to bias the valve element 66'downwardly toward engagement'with a resilient O-ring 74 carried on the inner wall of the passageway 68. The valve element 66* is inoved into and out of engagement with the O-ring 74 .to open and close thee'xhaust passageway 68.

To provide a means for operating the exhaust valve assembly 30 in accordance with the movement of the cylinder 20, a valve operator plate 75 is secured to the lower end of the valve element 66 by a nut 77. The outer edge of the plate 75 is adapted to be received in a recess '76 formed in the upper end of the cylinder 20. Thus, when the cylinder 20 moves to its normal position (FIG. 1), the cylinder 20 engages and "elevates the plate 75 against the action of the compression spring" to lift the valve element 66 out of engagementwith the O-ring .74. This places the interior of the cy1inder 20 in communication with the atmosphere through one or more openings a in the plate 75, the passageway 68 the opening 62', the recess 72, a bore 78 formed in the plug 60', "a plurality of radiallyextending passageways which are also formed in the plug 60 andone or more passage- 75 wa s 79 in the closure cap 26. Alternatively, when the To provide a means for slidably mounting the cylinder 7 stem and the Wall of the bore 4. 92 in the position shown in FIG. 1, compressed air from cylinder is shifted to its displaced position (FIG. 2), the upper end of the cylinder Ztl moves out of engagement with the valve operator plate 75 so that the compression spring 70 shifts the valve element 66 into engagement with the O-ring 74. This closes the passageway 68 to prevent compressed air in the chamber 16 from escaping to the atmosphere. Thus, the exhaust valve assembly 3% is selectively actuated to opened and closed conditions in accordance with the positions of the shifting cylinder 26.

Referring now more specifically to the piston 22, an upper flanged portion 22a thereof is slidably mounted within the cylinder 28, and a resilient 0-ring 82 carried on the flanged portion 22a seals the interface between the inner wall of the cylinder 2%} and the piston 22. The lower end of the piston 22 is slidably received within the chamber 14 and carries a resilient O-ring 84 for sealing the interface between the piston 22 and the wall of the chamber 14. The driver blade 24 is secured to the lower end of the piston 22 at a position msplaced from the axis thereof by an element 36 which is brazed or Welded to the driver blade 24'at its lower end and which is threaded at its upper end to be secured within an internally threaded aperture 83 formed in the lower end of the piston 22. Thus, the efiective length of the blade 24 can be adjusted by merely rotating this blade prior tothe insertion of the piston 22 into the tacker 1-13. Since the generally flat blade 24 is held against rotation by engaging the walls of the drive track shown in the above identified copending application and since the blade 24 is threadedly secured to the piston 22 at a point radially displaced from the axis thereof, relative rotary movement between the piston 22 and the blade 24 is prevented so as to prevent any change in the adjusted length of the. blade after the blade and the piston have been inserted into the tacker lit. The upper end of the piston 22 includes a recess 91) for receiving the lower end of the valve element as and the nut 77 so that the upperend of the piston 22 can engage the valve operator 75 to limit upward movement of the piston.

As indicated above, the safety valve assembly 32 and the manually actuated valve assembly 34 control the selective shifting of the position of the cylinder 20 so as to control the operation of the pneumatically actuated tool 10. These two valve assemblies are illustrated in part in the drawings and preferably are of the constructions disclosed in detail in the above identified copending Wandel and Doyle application. The safety valve assembly 32 includes a valve stem 92 that is slidably mounted within a bore 94 formed in the housing 12. An O-ring 99 carried on the stem 92 seals the interface between the With the valve stem the passageway 18 passes through the upper portion of the bore 94 and into the lower end of the chamber 16 through a port 96. When the valve stem 92 is elevated to the position illustrated in FIG. 2 by placing the nose of the tool 20 adjacent a workpiece, a recessed portion 98 on the stem 2 is moved into alignment with the port 96 and a passageway 16% so that compressed air now flows into the lower portion of the chamber 16 through a port 162, a portion of a bore 164;, the passageway 1%, the notched portion 98, and the port 95.

The port 102 and the bore 104 form a part of the manually controlled valve assembly 34. Thus, the actuation of the safety valve assembly 32 to the position shown in FIG. 2 places the operation of the tacker 10 under the control of this valve assembly. The manually controlled valve assembly 34 includes a sleeve 106 which is mounted within the lower end of the bore 104 and which is provided with an axially extending passageway 1%.. The passageway 198 is normally closed by a ball valve element 116 which is maintained in seating engagement with a resilient O-ring 112 by the pressure of the compressed air supplied through the port 192. However, when the ball valve 11b is lifted out of engagement with the O-ring 112 and into the position illustrated in FIG. 2 in which the port 162 is closed, the lower end of the chamber 16 is no longer supplied with compressed air from the passageway l8 and is connected to the atmosphere through the port 96, the notched portion 93, the passageway 100, the upper portion of the bore 104, and the passageway 168. Exhausting the lower portion of the chamber 16 shifts the cylinder 2% downwardly so that the exhaust valve assembly 30 is closed and compressed air is admitted to the upper end of the cylinder 20 to drive the piston 22 downwardly. When the tool 10 is lifted from the workpiece so that the valve stem 92 is restored to the position shown in FIG. 1 by resilient biasing means (not shown) or when the deflecting force is removed from the ball valve element 111 so that this element again engages the O-ring 112, compressed air is again supplied to the lower end of the chamber 16. This restores the cylinder 26 to the position illustrated in FIG. 1 and opens exhaust valve 3% so that the piston 22 can be elevated to the position shown in FIG. 1 by the compressed air supplied to the lower end of the chamber 16. Thus, the automatically actuated safety valve assembly 32 and the manually actuated valve assembly 34 control I the operation of the pneumatically actuated tool 10.

Referring now more specifically to the operation of the pneumatically actuated fastener driving tool it 111 the normal condition thereof compressed air is supplied from the reservoir defined by the hollow handle (not shown) through the enlarged passageway 13, the bore 94, and the port $6 to the lower end of the chamber 16. The compressed air admitted into the lower end of the chamber 16 is contained in the space bounded by the sealing O-rings 52, $2 and 34. This body of compressed air serves to hold the cylinder 29 in its normal position (PEG. 1) in which the upper end thereof engages the valve seat 28 to seal off communication between the chamber 16 and the upper end of the interior of the cylinder Further, in this normal position, thevalve operator plate 75 is engaged by the upper end of the cylinder 2b to open the exhaust valve assembly 3% so that the upper portion of the interior of thecylinder 24 is connected to the atmosphere. The upwardly directed component of force for maintaining the cylinder 20 in this normal position is due to the differential effective upper and lower areas on the cylinder 24 More specifically, since the annular area of the upper surface of the flange 20a on the cylinder 2% is connected to the atmosphere through the opening 54, the annular lower surfaces of the cylinder 2% and of the flanged portion Zita which are exposed to the compressed air is greater than the effective annular upper area of the upper end of the cylinder 29. Since both of these areas are exposed to compressed air of the same pressure, the greater eflective lower area produces an upwardly directed component of force for seating the upper end of the cylinder 29 on the valve seat 28 and for also overcoming the force applied to the cylinder by the compression spring 74 v The compressed air admitted to the lower end of the chamber 16 also serves to maintain the piston 22 'in its normal position adjacent the upper end of the cylinder 20. More specifically, the upper portion of the interior of the cylinder 2% is connected to the atmosphere through the exhaust valve assembly 3% which has been actuated to an open condition by the movement of the cylinder 29 to its normal position. The compressed air contained in the lower portion of the cylinder 2%) acts on the effective lower surface of the flanged portion 22a to provide an upwardly directed component of force which holds the upper end of the piston in engagement with the lower surface of the valve operator plate 75.

When the tool 1% is to be operated, the nose thereof is placed in engagement with a workpiece so that the safety' valve assembly 32 is actuated to move the valve stem 92 through the bore 94 to a position in'which the notched aosa 7 7 portion 98 is interposed between the passageway 10d and theport 96., In this position, the upper end of the valve stemf92 closes off communication between the bore 94 v 'maintained through the port 96, the notched portion 98 on the valve stem 92, the passageway 168, the upper end of the bore 104, and the port 162. A suitable manual control means, such as a trigger assembly, is then operated to move the ball yalve element 110 upwardly from the position'shown in FIG. 1 to the position shown in FIG. 2. In this position, the ball valve 116 closes the port 102 so that compressed air is no longer supplied to the lower end of "the chamber 16. In moving to this position, the ball valve element 11% moves out of engagement with the O-ring 112 so that the lower end of the' chamber 1 6 and the lower end of the interior of the cylinder 2! areconnected to the atmosphere through the port 96, the notched portion 98, the passageway 10%, a

pjortionoi the bore 104, and the passageway 163.

fWhen the lower end Oithe chamber 16 is returned to atmospheric pressure, the compressed'air in theupper portion cf the chamber 16 actingon the effective upper surface of the. cylinder 20 provides a downwardly directed component of force that moves the cylinder 20 downwardly until the lower end thereof engages the annularwall 42. This downward movement of the cylinder 20 operates the exhaust valve assembly 30 to a closed condition so as to prevent the compressedair in the upper portion of the chamber 16 from being exhausted to the atmosphere. More specifically, as the upperend ofv the cylinder 20 'moves downwardly to the position shown in FlGQ 2 and out of engagement with the valve operator plate 75, the compression spring 76 moves the valve element 66 downwardly until it engages the O-ring 74. This closes the passageway 68 to prevent communication between the'chamber 16 and the atmosphere.

When the upperend ot' the cylinder 29 moves out of engagement with the resilient valve seat 28, a large volume of air is abruptly admitted to the upper end. of the interior of the cylinder 26 to drive the piston 22 downwardly in 'a power stroke that'is terminated by the engagement of the lower end of the piston 22 with the resilient bumper 36; During this downward movement, the air entrapped in the lower end of the chamber 14 is exhausted through 'the openingw and'the air'entrapped in front of the flanged portion 22a of the piston 22 is 7 tween the annular wall 42 and the lower end of the cylinder 20, the lower end of the cylinder 20 can be provided with apertures or spaced notches to improve the fluid communication between the lower end of the chamber 16 and the interior of the cylinder 20 when the cylinder 20 is moved to the position illustrated in FIG. 2.

The tool 10 remains in the position shown in FIG. 2 until such time as only the safety valve assembly 32 or both the assembly 32 and the manually controlled valve assembly 34 are restoredto the condition shown in FIG. 1. At this time, compressed airis supplied to the lower end of the chamber 16 to again provide'an upwardly directed component of force which shifts the cylinder 26 upwardly until the upper end of this cylinder engages the resilient valve seat 28 to close off communication between the interior of the cylinder 20 and the upper portion of the chamber 16. During this upward movement, the

. valve operatoriplate 75 is engaged 'by the upper end of the cylinder20 and is moved upwardly against theforce of-the compression spring 7 I) so that the valve element 66 to the position illustrated in FIG. 1 in which the upper end thereof engages the valve operator plate '75. as a stop. As the piston 22 moves upwardly, the blade 24 is retracted in the drive track to permit the magazine assembly to advance the next fastenerto be driven into the drive track. Tlhus,'in response to each actuation of the valve assemblies 32 and 34, the piston 22 is driven through a single power stroke during which a fastener supplied to adrive track isgdriven into a workpiece.

.Although the present invention has been described in conjunction with a single embodiment thereof, it should be understood that numerous other modifications and embodiments may be provided by those skilled in the art which will fall within the spirit and scope of the principles cylinder movably mounted in said chamber and including a flanged portion in sliding engagement with the wall of said chamber, a piston slidably mounted in said cylinder, a valve seat normally engaged-"by said cylinder to prevent communication between said chamber and the interior of said cylinder, first means for continuously connecting one side of said flanged portion to the atmosphere,

,and second means including valve means ior selectively supplying compressed air to and exhausting compressed air trom the other side of said flanged portion to shift said cylinder into and out of engagement with said valve seat, thereby to provide means for selectively admitting compressed air from said chamber into said cylinder to drive 7 said piston.

2; In a fastener driving tool, a housing defining a chamber including an enlarged portion adapted to receive compressed air, a cylinder slidably mounted in said enlarged portion, a piston including a larger diameter upper portion slidably mounted in said cylinder and a lesser diameter lower portion slida bly mounted in said chamber, a fastener driving element secured to said lower portion of said piston 'and extending outwardly from said chamber, a 'valve seat normally engaged by the upper end of said cylinder to close ofi communication between the uper portion of the interior of said cylinder and the chamber, means for. shifting said cylinder relative to said valve seat to selectively admit compressed air from said chamber into the upper end of said cylinder to actuate said piston and said driving element, and means for selectively ladmitting'compressed air to the lower end of said cylinder between the upper and lower portions of said piston to provide means for retaining said piston to a position in proximity to said valve seat.

- a 3. In a fastener driving tool, a housing defining a chamber including a lower portion of lesser diameter and an upper portion ofgreater diameter to which compressed air can be supplied, a cylinder movably mounted in said greater diameter portion, a piston including a upper portion slidably mounted in said cylinder and a lower portion slidably mounted in said lesser diameter portion of said housing, a valve seat disposed adjacent the upper end of said'cylinder, first means for supplying compressed air to the lower end of the greater diameter portion of said chamber to force the upper end of said cylinder into engagement with said valve seat and to elevate said piston, and second'means for connecting the lower end of said greater diameter portion to the atmosphere to move said cylinder out of engagement with said valve seat so that compressed air in the upper end of said greater diameter portion of said chamber enters the upper end of said chamber and forces said piston downwardly.

4. In a fastener driving tool, a housing defining a chamber to which compressed air can be supplied, a cylinder mounted in said chamber for movement between first and second axially displaced positions, a valve seat carried on saidhousing adjacent the upper end of said cylinder and adapted to close the open upper end of said cylinder, a driver actuating piston movably mounted in said cylinder, valve means operable to a first setting forsupplying compressed air to the lower end of said chamber to force said cylinder to said first position in which the upper end of said cylinder engages said valve seat to close off communication between the interior ofsaid cylinder and said chamber, said valve means in said first setting also supplying compressed air into the lower end of said cylinder to elevate said piston within said cylinder, said valve means also being operable to a second setting in which the lower end of said cylinder is connected to the atmosphere to permit said piston to be moved downwardly and in which the lower end of said chamber is connected to the atmosphere to permit the compressed air in said chamber to move said cylinder into said second position in which the upper end of said cylinder is out of engagement with said valve seat, thereby admitting compressed air from said chamber into the upper end of said cylinder to drive said piston downwardly.

5. A fastener driving tool comprising a housing defining a pair of axially aligned cylindrical chambers of different diameters, the upper of said chambers having a greater diameter and being adapted to receive a body of compressed air, the lower of said chambers being of lesser diameter and being connected to said upper chamber by an annular wall formed in said housing; a cylinder slidably mounted in said upper chamber; a first sealing means carried on said cylinder in sliding engagement with said upper chamber; a piston slidably mounted in said two chambers and being of a length greater than the axial length of said upper chamber, said piston including an upper flanged portion slidably mounted in said cylinder and a lower portion slidably mounted in said lower chamber; second sealing means carried on said flanged portion in sliding engagement with said cylinder; third sealing means disposed between said lower portion of said piston and said lower chamber; a valve seat carried on said housing adjacent the upper end of said cylinder; and valve controlled means for selectively supplying compressed air to and exhausting compressed air from the two chambers in the space bounded by said first, second, and third sealing means to shift said cylinder relative to said valve seat and to reciprocate said piston relative to said cylinder.

6. The fastener driving tool set forth in claim in which said valve controlled means includes a passageway opening into said upper chamber adjacent said annular wall and in which said cylinder moves between two spaced positions, in one of which positions the upper end of said cylinder engages said valve seat and in the other of which positions the lower end of said cylinder engages said annular wall.

7. The fastener driving tool set forth in claim 5 including an exhaust valve assembly carried on said housing in communication with the interior of said cylinder, and means controlled by the shifting movement of said cylinder for operating said exhaust valve assembly.

8. In a fastener driving tool, a housing defining a chamber adapted to receive compressed air and having a first opening, a cylinder movably mounted within said chamber, a piston slidably mounted in said cylinder, a cap having a second opening and detachably mounted on said housing to close said first opening, a resilient valve seat adapted to be engaged by the upper end of said cylinder, an exhaust valve assembly mounted in said second opening for controlling communication between the interior of said cylinder and the atmosphere, means including said 1G exhaust valve assembly for securing said valve seat on said cap, and means for selectively moving said cylinder into and out of engagement with said valve seat.

9. In a fastener driving tool, a housing defining a chamber adapted to receive compressed air, a cylinder movably mounted in said chamber, a piston movably mounted in said cylinder, a valve seat normally engaged by the upper end of saidcylinder to close ofi communication between the interior of the cylinder and said chamber, means for shifting said cylinder into and out of engagement with said valve seat to selectively admit air into said cylinder to operate said piston, saidhousing also providing an exhaust passageway opening into said chamber in a position aligned with said cylinder, valve means, resilient means biasing said valve means toward a position closing said passageway, and a valve operator connected to said valve means and positioned between said valve seat and said cylinder in the path of movement of said cylinder to opcrate said valve means to a position opening said passageway in repsonse to movement of said cylinder toward said valve seat.

10. In a fastener driving tool, a housing defining a chamber having an upper opening and adapted to receive compressed air, a cylinder movably mounted in said chamber, a piston movably mounted in said cylinder, a cap mounted on said housing to close said opening and including an exhaust passageway, valve means carried on said cap, resilient means biasing said valve means to a position closing said passageway, a valve seat fixedly secured to said cap and normally engaged by said cylinder to close oif communication between the interior of the cylinder and said chamber, means for shifting said cylinder toward and away from said valve seat to move said cylinder into and out of engagement with said valve seat to selectively admit air into said cylinder to operate said piston, and means connected to said valve means and actuated by engagement with said cylinder during movement of said cylinder toward engagement with said valve seat for moving said valve means against said resilient means to a position opening said passageway.

11. In a fastener driving tool, a housing defining a chamber adapted to receive compressed air, a valve seat carried on said housing, a cylinder mounted in said chamber and movable into and out of engagement with said valve seat to control communication between said chamber and the interior of said cylinder, a piston slidably mounted in said cylinder, means for shifting said cylinder to move the upper end of said cylinder out of engagement with said valve seat to permit the compressed air in said chamber to drive said piston and for shifting the upper end of said cylinder into engagement with said valve seat, an exhaust valve carried on said housing and including an inlet aligned with the interior of said cylinder, resilient means continuously urging said exhaust valve to a closed condition, and a valve operator secured to said exhaust valve and disposed in the path of movement of said cylinder to be engaged by the upper end of said cylinder when the upper end of the cylinder engages said valve seat, engagement of said valve operator by said cylinder maintaining said exhaust valve in an open condition in which the interior of said cylinder is connected to the atmosphere.

12. In a fastener driving tool, a housing defining a chamber having an opening and adapted to be supplied with compressed air, a cylinder movably mounted in said chamber, a piston including at least a portion slidably mounted in said cylinder, a cap mounted on said housing in axial alignment with said cylinder and closing said opening, a resilient valve seat carried on said cap and adapted to be engaged by the upper end of said cylinder to prevent communication between the exterior of said cylinder and the chamber, means for shifting said cylinder out of engagement with said valve seat to admit compressed air from said chamber to drive said piston and for then shifting said cylinder into engagement with 1 1 said valve seat to entrap compressed air withinsaid cylinder between said cap and said piston, said cap including means defining a passageway extending betweentheinterior of said cylinder and the atmosphere, valve means for controlling the'flow of air throug id passageway; resilient means normally urging said valve means toward a closed position to prevent communication between the atmosphere and the chamBer, and valve operator means connected to said valve means and adapted to be, engaged by the upper end of said cylinder, said resilient means closing said valve means in response to said cylinder moving away from said valve seat and said valve operator means opening said valve means to exhaust the compressed entrapped in said cylinder in response tothe upper i2 end of said cylinder engaging saidlvalve opera-terminus when said cylinder moves toward said valve seat.

V I References Cited in the died is patent if,

UNITED STATES PATENTS- 

